1. Field of the Invention
The present invention relates to halogen gas plasma-resistive members to be used as chamber walls and roofs in semiconductor-producing apparatuses.
2. Related Art Statement
In the semiconductor-producing apparatuses requiring the super clean state, halogen-based corrosive gases such as chlorine-based gases and fluorine-based gases are used as depositing gases, etching gases and cleaning gases.
For example, a semiconductor-cleaning gas composed of a halogen-based corrosive gas such as ClF3, NF3, CF4, HF or HCl is used in the semiconductor-producing gas such as a hot CVD apparatus. In the depositing stage, the halogen-based corrosive gas such as WF6 or SiH2Cl2 is used as a film-forming gas.
Further, corrosion gases such as CF-based gases, oxygen, chlorine-based gases, and bromine-based gases are also used in etching apparatuses.
There is recently a tendency that a particularly highly corrosive gas such as NF3 is used to increase the etching speed. Owing to this, there is a problem that wall surfaces of chambers of the semiconductor-producing apparatuses are corroded to form particles, and such particles falls on wafers. Further, it may be that a reaction product deposited on the wall surface is peeled and falls on wafers as particles. This causes poor insulation and poor conduction phenomena, resulting in poor semiconductors. Accordingly, a technique for preventing the transfer of the particles onto the wafers from the wall surfaces of the chambers or roofs has been demanded.
It is an object the present invention to provide a halogen gas plasma-resistant member to be exposed to halogen gas plasma, which member suppresses the floating in a space inside a container and falling and depositing on other members in the container of particles formed by corrosion of the members and with worked dust of wafers.
Further, there is known a technique that a chamber or a dome is made of a ceramic material such as alumina, and its surface is coated with a corrosion-resistant film. In this case, however, it is indispensably required to prevent occurrence and falling of the above-mentioned particles and to suppress the peeling of the corrosive-resistant film. It is indispensable that the corrosive-resistant film does not peel and firmly adheres to the surfaces of the chamber or the dome even after application of a number of heat cycles particularly under an environment where the corrosive-resistant film contacts with the corrosive material.
A first aspect of the present invention is directed to a halogen gas plasma-resistant member to be exposed to a halogen gas plasma, comprising a main body of said member, and a corrosion-resistant film formed on at least a surface of said main body, wherein a relative density of the corrosion-resistant film is not less than 90%, preferably not less than 95%, and a peeling resistance of the corrosive film to said main body is not less than 15 MPa.
A first aspect of the present invention is also directed to a halogen gas plasma-resistant member to be exposed to a halogen gas plasma, comprising a main body of the member, and a corrosion-resistant film formed on at least a surface of said main body, wherein a relative density of the corrosion-resistant film is not less than 90%, preferably not less than 95%, and a center-line average surface roughness Ra of the corrosion-resistant film is not less than 1.2 xcexcm.
The present inventors discovered that floating in a space inside a container and falling and depositing on other members in the container of particles formed by corrosion are suppressed by forming the corrosive-resistant film having the relative density and the peeling resistance as mentioned above on the surface of the main body of the member. It is probably considered that an increase in the peeling resistance of the film reduces the peeling of the corrosion-resistant film form the main body and thus decreases the particles. The inventors further discovered that the above peeling resistance needs to be substantially not less than 15 MPa so as to prevent the formation of the particles.
Furthermore, the present inventors discovered that floating in the space inside a container and falling and depositing on other members in the container of particles formed by corrosion are suppressed by forming the corrosive-resistant film having the relative density and the Ra as mentioned above on the surface of the main body of the member.
It is considered that the corrosion-resistant film functions to suppress the formation of the particles, and that even if a small amount of particles formed by corrosion and working wafers are maintained on the surface of the corrosion-resistant film, increasing the relative density of the corrosion-resistant film, reducing pores in the surface and increasing the Ra (retaining unevenness at the surface) as mentioned above, thereby avoids the floating in the space and falling and depositing on other members of the particles.
The large surface roughness Ra of the corrosive-resistant film means that uneven portions remain at the surface of the film. When the surface is microscopically viewed, there are recesses and their adjacent projections. The projections are made of particles that project from adjacent recesses. Therefore, it was considered that when the Ra of the surface of the corrosion-resistant film is increased, the halogen gas plasma enters the recesses at the surface, grain boundaries are corroded from root portions of the projections (particles), and thus the formation of the particles is promoted. However, the larger Ra contributes less to the increase in such particles, but on the contrary prevents the floating in the space inside the container and falling of the particles.
From the above standpoint, the center-line average surface roughness of the corrosion-resistant film is preferably not less than 3 xcexcm. Since too large Ra promotes the corrosion of the surface of the corrosion-resistant film and thus increases the particles, Ra is preferably not more than 20 xcexcm from this point of view, more preferably not more than 8 xcexcm. The relative density of the corrosion-resistant film is preferably not more than 95%.
The waveness Wa of the corrosion-resistant film is preferably not less than 1 xcexcm. As a matter of course, there is no such limitation in a case where a byproduct is produced as a gas phase according to some processes, which does not form a solid matter such as particles. In this case, the surface roughness is preferably not more than 1.5 xcexcm, more preferably not more than 1.0 xcexcm. In this case, the relative density of the corrosion-resistant film is preferably not less than 90%, more preferably not less than 95%.
The corrosion-resistant film is preferably free from cracks having lengths of not less than 3 xcexcm and/or widths of not less than 1 xcexcm.
It can be confirmed by a scanning type electron microscope at not less than 5000 times magnification whether the corrosion-resistant film is free from such microcracks or not.
An underlying face for the corrosion-resistant film is preferably porous. The center-line average surface roughness Ra of the underlying face of the corrosion-resistant film is preferably not less than 1.2 xcexcm, and more preferably not less than 1.5 xcexcm. In that case, the adhesion of the corrosion-resistant film to the underlying face can be enhanced, and production of particles due to the peeling of the film can be prevented.
In order to coarsen the underlying face, the underlying face may be made porous or the underlying face may be processed by grain polishing or sand blasting.
It is a second aspect of the present invention to provide a laminate comprising a substrate made of alumina and a film formed on the substrate, in which the film is hard to be peeled from the substrate and the film is hard to be peeled even after the film contacts a corrosive material.
The second aspect of the present invention is also to provide a corrosion-resistant member having high corrosion resistance and long-term stable usability with use of this laminate, particularly a halogen gas plasma-resistive member.
The second aspect of the present invention is directed to a laminate comprising a substrate made of alumina, and a film of a yttrium compound formed on the substrate, wherein a reaction product between alumina and yttrium compound exists along an interface between the substrate and the yttrium compound film.
The present inventors discovered that when a film of the yttrium compound is formed on the alumina substrate by a special producing method mentioned later, the reaction product between the alumina and the yttrium compound is produced along the interface between them depending upon producing conditions. The inventors also discovered that when such a reaction product is produced, the film of the yttrium compound is not peeled even after heat cycles are applied, for example, between 800xc2x0 C. and room temperature.
This reaction product is usually produced in a filmy form along the interface between the substrate and the yttrium compound, and constitutes an intermediate layer. This layer-like form of the reaction product may be continuous over the entire interface between the substrate and the yttrium compound, may be discontinuously formed at the interface between the substrate and the yttrium compound or may be formed in the form of plural layer-like islands. In this case, such layer-like islands do not continue to one another, but they exist in a layered form along the interface and constitute an intermediate layer, when viewed as a whole. The present invention includes cases where the reaction product exists in a dotted manner or are scattered at the interface between the substrate and the yttrium compound. The present invention includes such cases where the reaction product with a totally small area exists in the dotted manner or are scattered. Further, so long as the above reaction product is confirmed by an X-ray diffraction device, those cases fall in the scope of the present invention.
These and other objects; features and advantages of the invention will be appreciated upon reading the following description of the invention when taken in conjunction with the attached drawings, with the understanding that some modifications, variations and changes of the invention could be easily made by the skilled person in the art to which the invention pertains.